Okay - I've got the integrated trailer brake controller maxed out again, and the trailer brakes barely pull back on the truck.

Dealer checked the ITBC again, and its now performing to spec, so the problem has to be with the trailer.

Trailer is a trip axle 5th wheel, electric only brakes. About 3 years old and maybe 10K hwy miles if it makes a difference.

Where should I start looking, and how can I increase the braking force on my trailer? I'm pretty proficient with testers and meters, so what should I look for?

Possibly too much voltage drop present at the magnets on the axles? Some trailer's wiring is not up to par and results in poor performance. Might try checking the voltage at the magnets.

Check your trailers ground. It's 50% of the equation.

If you have a set of booster cables use them to form two temporary grounds between the truck and the trailer. Try the brakes then.

Check your trailers ground. It's 50% of the equation.

If you have a set of booster cables use them to form two temporary ground between the truck and the trailer. Try the brakes then.

Thats a good idea and a neat tip- I'll have to put that one to use sometime.

Thats a good idea and a neat tip- I'll have to put that one to use sometime.

I towed about 1000 Kilometers a few years ago with a set of booster cables clamped between my pinbox on the 5er and the hitch in the bed after I broke a ground wire under the truck somewhere.

Worked like a charm.

Good diagnostic tool as well, quick and easy. :)

Even if you have self adjusting brakes, closely check the adjustment on every wheel. Also check for broken wires to the magnet at each wheel. Finally, have someone engage the brakes and listen at each wheel for the magnet to grab the drum (you can hear it engage).

I would agree with checking the trailer brakes, most are supposed to be adjusted within 3,000 miles initally. Could be they just need that inital adjustment. Also if you know someone else with a trailer that will let you drag it around the block would be worth a try.

x2 on trailer brake adjustment

I had all the backing plates replaced on my 1st toyhauler, and that seemed to end my "weak braking" problem. Yours seems to be used a lot less to this point though.

I use to fix brakes for a living years ago. Drum brakes don't self adjust if they are dirty or if the adjusters rust. It sounds like its time to pull all the wheels and clean and adjust the brakes by hand. Make sure you repack the wheel bearing and put in new grease seals. Pump the brake peddle a few times when you put it all back together to seat the brake shoes. I adjusted my brakes so the wheel spins about 3 full turns when you spin it before it stops.

Pump the brake peddle a few times when you put it all back together to seat the brake shoes. I adjusted my brakes so the wheel spins about 3 full turns when you spin it before it stops.

Electric actuated drums- no pedal here.

I've adjusted the brakes on each wheel so that they lightly drag with no braking force.

I'll check the ground next - did you mean ground on the truck or ground on the trailer?

How do you measure voltage across the magnets? Line in and ground?

The ground between the truck and trailer. The positive side of the trailer brake wire may be fine, but if the ground between the truck and trailer is poor you wont be able to get proper amperage to the brake magnets. Low amps equals low magnet clamping force, equals poor braking action.

I've adjusted the brakes on each wheel so that they lightly drag with no braking force.

I'll check the ground next - did you mean ground on the truck or ground on the trailer?

How do you measure voltage across the magnets? Line in and ground?


Alko Axle Manual PDF -see page 17 for magnet tests
http://www.al-kousa.com/pdf/alkobrochure.pdf

Update - I checked all the wiring and grounds - magnets working fine. I found the master ground was through a product called a "short stopper" I pulled it out and checked continuity and resistance and sure enough - 6-7 ohms. Looks like some cheap Chinese electrical part sourced from the lowest bidder.

I left it out and re-grounded the trailer and now the brakes work MUCH better than before. I feel like I could actually panic stop a full load now if I had to. I hope there isn't any drawback to leaving this thing out.

Thanks to all for the help and advice.

One further question though - is there a reason the brakes don't ground to the frame as soon as they leave the wheels? There is wiring to and from the brake drums all the way up to the junction box in the pinbox. I would think using the frame as the ground path would improve conductivity.

One further question though - is there a reason the brakes don't ground to the frame as soon as they leave the wheels? There is wiring to and from the brake drums all the way up to the junction box in the pinbox. I would think using the frame as the ground path would improve conductivity.

Frame grounds are much less reliable versus dedicated wiring run straight to the point. As the trailer gets older and rust more prevalent, things that rely on frame grounds have a habit of failing, or getting intermittent/cranky.

When it comes to critical things like brakes you can't have dodgy performance. Dedicated grounds run straight to the electrical plug rule out any problems with poor grounding.

Of course, when the manufacturer puts some junk electrical piece and creates a weak link in the chain, it's all rather moot. :rolleyes: Glad you found the problem!